IPFW is is a native firewall built into FreeBSD.

IPFW is a stateful firewall included in the basic FreeBSD install as a kernel loadable module and supports both IPv4 and IPv6. It is comprised of several components: the kernel firewall filter rule processor and its integrated packet accounting facility, the logging facility, NAT, the dummynet(4) traffic shaper, a forward facility, a bridge facility, and an ipstealth facility.